Python 3.15 有什么新变化

编者:

Hugo van Kemenade

本文介绍了 Python 3.15 相比 3.14 的新增特性。

详情请参阅 更新日志。

备注

预发布版用户应当了解到此文档目前处于草稿状态。 它将随着 Python 3.15 的发布进程不断更新，因此即使已经阅读过较早的版本也仍然值得再次查看。

摘要 -- 发布重点

新的特性

PEP 810: 显式惰性导入

大型 Python 应用程序经常会有启动时间缓慢的困扰 。此问题有很大一部分是来自导入系统：当一个模块被导入时，Python 必须定位文件，将其从磁盘读入，将其编译为字节码，并执行全部的最高层级代码。 对于具有较深依赖树的应用程序来说，此过程耗时将以秒计，即使在大部分被导入代码在某次运行期间从未被实际使用时也是如此。

开发者要绕过此问题可通过将导入移至函数内部，使用 importlib 按需加载模块，或重新调整代码结构以避免不需要的依赖项。 这些方式有一定效果但会使代码变得更难阅读和维护，使代码库中的 import 语句到处零星散布，并需要严格制定规则才能持续应用。

Python 现在会使用新的 lazy 软关键字通过显式的 lazy 导入提供一种更清晰的解决方案。Python 将延迟实际的模块加载直到所导入的名称首次被使用。 这在组织方面给予你在文件顶部声明所有导入的便利同时只付出你实际使用模块的加载耗时。

lazy 关键字同时适用于 import 和 from ... import 语句。 当你使用 lazy import heavy_module 的写法时，Python 不会立即加载该模块。 作为替代，它将创建一个轻量的代理对象。 实际的模块加载会在你首次访问该名称时透明地发生：

lazy import json
lazy from pathlib import Path

print("Starting up...")  # json 和 pathlib 尚未加载

data = json.loads('{"key": "value"}')  # json 在这里加载
p = Path(".")  # pathlib 在这里加载

这种机制特别适用于在最高层级导入大批模块但在任何给定运行中仅使用它们的一个子集的应用程序。 延迟加载可减少启动反应时间而无需代码重新调整结构或在代码库中零散使用有条件的导入。

对于加载惰性导入模块失败的情况（例如，当模块不存在时），Python 会在首次使用时而不是导入时引发异常。 相关的回溯将同时包括名称被访问的位置和初始的 import 语句，以使对失败的诊断和调试更为直观。

对于在你希望全局启用惰性加载而不必修改源代码的场景，Python 提供了 -X lazy_imports 命令行选项和 PYTHON_LAZY_IMPORTS 环境变量。 两者均接受两种值: all 使所有导入默认为惰性的，而 normal (缺省值) 将遵循源代码中的 lazy 关键字。 sys.set_lazy_imports() 和 sys.get_lazy_imports() 函数现在允许在运行时修改和查询此模式。

想要更有选择性的控制，sys.set_lazy_imports_filter() 接受一个可调用对象决定是否应惰性加载特定的模块。 该过滤器接收三个参数：要导入模块的名称 (或 None)，已导入模块的名称，以及 fromlist （或 None 表示用于常规导入）。它应返回 True 表示允许惰性导入，或 False 表示以强制立即加载。 这将允许只让你自己的应用的模块采用惰性导入而而让第三方依赖项采用立即导入的模式：

import sys

def myapp_filter(importing, imported, fromlist):
    return imported.startswith("myapp.")
sys.set_lazy_imports_filter(myapp_filter)
sys.set_lazy_imports("all")

import myapp.slow_module  # 惰性（匹配过滤器）
import json               # 立即（不匹配过滤器）

对于需要以编程方式检测惰性导入的代码来说代理类型本身可通过 types.LazyImportType 访问。

在哪里可以使用 lazy 关键字是有一些限制的。 惰性导入仅在模块作用域上被允许；在函数、类语句体或 try/except/finally 语句块中使用 lazy 会引发 SyntaxError。 星号导入和 future 导入都不能是惰性的 (lazy from module import * 和 lazy from __future__ import ... 都会引发 SyntaxError)。

对于无法直接使用 lazy 关键字的代码（例如，在要支持早于 3.15 的 Python 版本而仍使用 3.15+ 的惰性导入时），一个模块可以定义 __lazy_modules__ 作为完整限定名称字符串的容器。 用于这些模块的常规 import 语句就会被视为惰性的，具有与 lazy 关键字一样的语义:

__lazy_modules__ = ["json", "pathlib"]

import json     # 惰性
import os       # 仍为立即型

参见

完整规范说明及考量见 PEP 810。

（由 Pablo Galindo Salgado 和 Dino Viehland 在 gh-142349 中贡献。）

PEP 814: 增加 frozendict 内置类型

在 builtins 模块中增加了一个新的 immutable 类型 frozendict。 它在创建之后就不允许修改。 frozendict 不是 dict 的子类；它直接继承自 object。 一个 frozendict 在它的键与值都是可哈希对象的情况下就将是 hashable 对象。 frozendict 会保持其插入顺序，但在比较时不会将顺序纳入考虑。

例如:

>>> a = frozendict(x=1, y=2)
>>> a
frozendict({'x': 1, 'y': 2})
>>> a['z'] = 3
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    a['z'] = 3
    ~^^^^^
TypeError: 'frozendict' object does not support item assignment
>>> b = frozendict(y=2, x=1)
>>> hash(a) == hash(b)
True
>>> a == b
True

下述标准库模块已对应更新到接受 frozendict: copy，decimal，json，marshal，plistlib (仅在序列化时)，pickle，pprint 和 xml.etree.ElementTree。

eval() 和 exec() 接受 frozendict 作为 globals，而 type() 和 str.maketrans() 接受 frozendict 作为 dict。

通过 isinstance(arg, dict) 检测 dict 类型的代码可以更新为 isinstance(arg, (dict, frozendict)) 以同时接受 frozendict，或更新为 isinstance(arg, collections.abc.Mapping) 以接受包括 MappingProxyType 在内的其他映射类型。

参见

完整规范说明及考量见 PEP 814。

（由 Victor Stinner 和 Donghee Na 在 gh-141510 中贡献。）

PEP 661: 增加 sentinel 内置类型

在 builtins 模块中新增 sentinel 类型用于创建带有精确表示的哨兵值。 哨兵对象在拷贝时会保留其标识号，支持在类型表达式中的 | 运算符，并在它们按模块和名称导入时可以被封存。

（PEP 由 Tal Einat 撰写；由 Jelle Zijlstra 在 gh-148829 中贡献。）

参见

更多细节参见 PEP 661。

PEP 799: 专用的性能分析包

新增的 profiling 模块将 Python 的内置性能分析工具整合到单独的、统一的命名空间中。 该模块包含：

cProfile 模块仍作为一个别名保留用于向下兼容。 profile 模块已被弃用并将在 Python 3.17 中移除。

参见

详情见 PEP 799。

（由 Pablo Galindo 和 László Kiss Kollár 在 gh-138122 中贡献。）

Tachyon: 高频统计型采样性能分析器

Tachyon 性能分析器标志

新增一个采样型性能分析器 (Tachyon) 并以 profiling.sampling 作为模块。 此性能分析器将为运行中的 Python 进行启用低开销的性能分析而无需代码修改或进程重启。

不同于测量每次函数调用的确定型性能分析器 (如 profiling.tracing)，采样型性能分析器会定期捕获来自运行中进程的栈追踪信息。 此方式可在实际零开销的情况下获得 最高 1,000,000 Hz 的采样率，使其成为 Python 中目前（在其发布时）最快的采样型性能分析器并适用于解决生产环境下的调试性能问题。 这种能力对于传统性能分析方式侵入性过高的生产系统的调试性能问题是理想的解决方案。

关键特性包括：

  • 零开销性能分析: 附加到任何运行中的 Python 进程而不影响其性能。 对于不便重启或减慢的应用程序的生产环境调试来说非常理想。

  • 无需代码修改: 对现有应用程序进行性能分析不必重启。 只需简单地将性能分析器按 PID 指向运行中的进程并开始收集数据。

  • 灵活的目标模式:

    • 按 PID 对运行中的进程进行性能分析 (attach) - 附加到已运行的应用程序

    • 直接运行脚本并进行性能分析 (run) - 从最初执行位置开始性能分析

    • 执行模块并进行性能分析 (run -m) - 通过运行 python -m module 对包进行性能分析

    • 抓取运行中的进程的一次性快照 (dump) - 打印每个线程的回溯风格栈信息（或使用 --async-aware 则为所有的 asyncio 任务）。 适用于调查挂起的进程。

  • 多重性能分析模式: 基于你的性能调查选择衡量指标：

    • 挂钟时间 (--mode wall, 缺省值): 衡量真实花费时间包括 I/O, 网络等待和阻塞型操作。 使用此模式了解你的程序的实际耗时花费在哪里，包括对外部资源的等待。

    • CPU 时间 (--mode cpu): 仅衡量激活的 CPU 执行时间，不包括 I/O 等待和阻塞。 使用此模式来确定 CPU 密集型瓶颈并优化计算工作。

    • GIL 持有时间 (--mode gil): 衡量在持有 Python 的全局解释器锁的情况下花费的时间。 使用此模式来确定在多线程应用程序中哪个线程主导了 GIL 的使用。

    • 异常处理时间 (--mode exception): 仅捕获来自有激活异常的线程的采样。 使用此模式来分析异常处理的开销。

  • 线程感知性能分析: 选择对所有线程 (-a) 或是只对主线程进行性能分析，在分析多线程应用程序行为时非常关键。

  • 多种输出格式: 选择最适合你的工作流程的可视化：

    • --pstats: 与 pstats 兼容的详细表格型统计。 显示包含直接和累积采样的函数级耗时。 适用于详细分析以及与现有 Python 性能分析工具的集成。

    • --collapsed: 生成展开的栈追踪信息（每个栈一行）。 此格式专门设计用于通过外部工具如 Brendan Gregg 的 FlameGraph 脚本或 speedscope 来创建火焰图。

    • --flamegraph: 使用 D3.js 生成自包含的交互式 HTML 火焰图。 直接在你的浏览器中打开进行即时可视化分析。 火焰图将显示调用层级结构其中宽度代表耗费的时间，可以很容易地一眼找出性能瓶颈。

    • --gecko: 生成与 Firefox Profiler 兼容的 Gecko Profiler 格式。 将输出上传到 Firefox Profiler 用于基于时间线的分析包括栈图表、标记和网络活动等高级特性。

    • --heatmap: 生成带有行级采样计数的交互式 HTML heatmap 可视化形式。 创建一个目录包含显示源代码层级时间耗费位置的每个 heatmap 文件。

  • 实时交互模式: 具有与 top 类似界面的实时 TUI 性能分析器 (--live)。 使你的应用程序在带有交互式排序和过滤的情况下运行并监视执行效率。

  • 异步感知性能分析: 使用基于任务的栈重建对 async/await 代码进行性能分析 (--async-aware)。 查看哪些协程最为耗时，并可选择只显示运行中的任务或全部任务包括等待中的任务。

  • 操作码级性能分析: 收集字节码的操作码信息用于在指令层级进行性能分析 (--opcodes)。 显示哪些字节码指令正在执行，包括来自适配解释器的专门化。

请参阅 profiling.sampling 获取完整文档，包括所有可用的输出格式、性能分析模式以及配置选项。

（由 Pablo Galindo 和 László Kiss Kollár 在 gh-135953 和 gh-138122 中贡献。）.)

PEP 831: 默认启用帧指针

现在 CPython 会在受支持的平台上默认附带帧指针进行构建。 这将使用编译器旗标 -fno-omit-frame-pointer 和 -mno-omit-leaf-frame-pointer，使得原生栈展开更快速且对系统性能分析器、调试器、崩溃分析工具和基于 eBPF 观察能力工具来说更可靠。

这些旗标是通过 sysconfig 对外暴露的，因此由使用 Python 构建配置的工具所构建的扩展模块默认会继承帧指针。 这样的传播是有意设计的：混合 Python 与原生性能分析需要一个跨解释器、扩展模块、嵌入应用程序以及原生库的连续帧指针链。

重要

第三方构建后端和原生构建系统应当在它们使用 Pytho 的 sysconfig 值时保留这些旗标。 编译 C, C++, Rust 或其他原生代码而不继承 Python 的编译器旗标的构建系统应当自行启用等价的帧指针旗标。 只要有一个构建时不带帧指针的原生组件就可能破坏整个 Python 进程的栈展开。

（由 Pablo Galindo Salgado 和 Savannah Ostrowski 在 gh-149201 中贡献；PEP 831 由 Pablo Galindo Salgado, Ken Jin, Savannah Ostrowski 和 Diego Russo 撰写。）

参见

更多细节参见 PEP 831。

PEP 798: 推导式中的解包

列表、集合与字典推导式，以及生成器表达式现在都支持使用 * 和 ** 进行解包。 这将 PEP 448 的解包语法扩展到推导式，提供了将任意多个可迭代对象或字典合并至一个展平的结构的新语法。 这种新语法是嵌套推导式, itertools.chain() 和 itertools.chain.from_iterable() 等的直接替代物。 例如:

>>> lists = [[1, 2], [3, 4], [5]]
>>> [*L for L in lists]  # 等价于 [x for L in lists for x in L]
[1, 2, 3, 4, 5]

>>> sets = [{1, 2}, {2, 3}, {3, 4}]
>>> {*s for s in sets}  # 等价于 {x for s in sets for x in s}
{1, 2, 3, 4}

>>> dicts = [{'a': 1}, {'b': 2}, {'a': 3}]
>>> {**d for d in dicts}  # 等价于 {k: v for d in dicts for k,v in d.items()}
{'a': 3, 'b': 2}

生成器表达式可以类似地进行解包从多个可迭代对象产生值:

>>> gen = (*L for L in lists)  # 等价于 (x for L in lists for x in L)
>>> list(gen)
[1, 2, 3, 4, 5]

这项改变也将扩展至异步生成器表达式，举例来说，它使得 (*a async for a in agen()) 等价于 (x async for a in agen() for x in a)。

参见

详情见 PEP 798。

（由 Adam Hartz 在 gh-143055 中贡献。）

PEP 829: 包启动配置文件

当未给出 -S 时将由 site 模块加载，.pth 文件 可包含同时扩展 sys.path 和以 import 打头（跟一个空格或制表符）时执行任意代码的行。 后者的功能可能存在问题，因为难以确定在 Python 启动时会执行什么。

作为提升对预启动可执行代码审计能力的一个步骤，Python 3.15 引入了包含 pkg.mod:callable 形式的入口点规格说明的 .start 文件 其中 pkg.mod 是给定可调用对象的导入路径。 当 Python 启动时，将定位可调用对象并不带参数地进行调用。

在 .pth 文件中的添加 import 行的做法已被静默地弃用。 当找到匹配 .start 文件时，.pth 文件中的 import 行将被忽略。 .pth 文件中的 sys.path 扩展行没有改变。

site 模块还提供了 site.StartupState 用于多个 site 目录的批量启动处理，以确保所有静态路径扩展在执行任何启动代码之前被应用。 site.main() 会隐式地使用该类的实例在正常的解释器启动期间批量处理所有启动配置文件。 需要相同批处理行为的调用者可以直接构建一个 StartupState 并通过 addsitedir(), addusersitepackages() 和 addsitepackages() 驱动它，然后在批处理结束时调用 process() 一次。

（由 Barry Warsaw 在 gh-148641 和 gh-150228 中贡献。）

PEP 803 -- 自由线程构建版的稳定 ABI

以 稳定 ABI 作为目标的 C 扩展现在可以针对新的 自由线程构建版稳定 ABI (或称 abi3t) 进行编译，这将使其能兼容 CPython 的 自由线程构建版。 这通常需要对源代码进行不小的更改；具体而言：

请注意稳定 ABI 并未提供 CPython 所必须提供的所有功能。 无法切换至 abi3t 的扩展应当继续分别针对现有的稳定 ABI (abi3) 以及自由线程版本专属 ABI (cp315t) 进行构建。

针对自由线程构建版的稳定 ABI 通常应当在构建工具中选择（例如 Setuptools, meson-python, scikit-build-core 或 Maturin 之类）。 在编写时，这些工具 并不 支持 abi3t。 如此你的工具也是这种情况，则要为 cp315t 单独编译。 如果你没有使用构建工具 -- 或是正在编写这样的工具 -- 你可以像在 针对稳定 ABI 编译 中介绍的那样通过设置宏 Py_TARGET_ABI3T 来选择 abi3t。

一份关于切换到 abi3t 的实用 迁移指南。

参见

更多细节参见 PEP 803。

PEP 788: 围绕解释器终结化对 C API 的保护

在 C API 中，解释器终结化 对许多扩展来说都是一个问题，因为 附加 线程状态会永久性地挂起线程，导致死锁和其他出错问题。 此外，历史上在使用一个解释器之前安全地检测它是否激活是不可能的，当一个线程并发地删除另一个线程正尝试附加的解释器时会造成程序崩溃。

现在有几个新的 API 套件可以绕过这些问题：

  • 解释器守卫，它可以阻止解释器被终结。

  • 解释器视图，它允许线程安全地访问可能被并发地终结或删除的解释器。

  • 具有内置防终结保护的 新 API 用于自动附加和分离线程状态。

此外 PyGILState 族中的 API (最主要的是 PyGILState_Ensure() 和 PyGILState_Release()) 已被设为 soft deprecated。 目前 没有 移除它们的计划，现有的代码将继续可用，但在未来的 Python 版本中将不会有新的 PyGILState。

参见

详情见 PEP 788。

（由 Peter Bierma 在 gh-149101 中贡献。）

改进的错误消息

  • 现在当访问的属性不存在于某个对象上，但类似的属性可通过它的某个成员访问时解释器会在 AttributeError 异常中提供更有帮助的建议。

    举例来说，如果对象具有的一个属性本身暴露了所请求的名称，错误消息将建议通过该内部属性来访问它：

    @dataclass
class Circle:
   radius: float

   @property
   def area(self) -> float:
      return pi * self.radius**2

class Container:
   def __init__(self, inner: Circle) -> None:
      self.inner = inner

circle = Circle(radius=4.0)
container = Container(circle)
print(container.area)

    Running this code now produces a clearer suggestion:

    Traceback (most recent call last):
  File "/home/pablogsal/github/python/main/lel.py", line 42, in <module>
    print(container.area)
          ^^^^^^^^^^^^^^
AttributeError: 'Container' object has no attribute 'area'. Did you mean '.inner.area' instead of '.area'?

  • When an AttributeError on a builtin type has no close match via Levenshtein distance, the error message now checks a static table of common method names from other languages (JavaScript, Java, Ruby, C#) and suggests the Python equivalent:

    >>> [1, 2, 3].push(4)
Traceback (most recent call last):
...
AttributeError: 'list' object has no attribute 'push'. Did you mean '.append'?

>>> 'hello'.toUpperCase()
Traceback (most recent call last):
...
AttributeError: 'str' object has no attribute 'toUpperCase'. Did you mean '.upper'?

    When the Python equivalent is a language construct rather than a method, the hint describes the construct directly:

    >>> {}.put("a", 1)
Traceback (most recent call last):
...
AttributeError: 'dict' object has no attribute 'put'. Use d[k] = v.

    When a mutable method is called on an immutable type, the hint suggests the mutable counterpart:

    >>> (1, 2, 3).append(4)
Traceback (most recent call last):
...
AttributeError: 'tuple' object has no attribute 'append'. Did you mean to use a 'list' object?

    These hints also work for subclasses of builtin types.

    (Contributed by Matt Van Horn in gh-146406.)

  • The interpreter now tries to provide a suggestion when delattr() fails due to a missing attribute. When an attribute name that closely resembles an existing attribute is used, the interpreter will suggest the correct attribute name in the error message. For example:

    >>> class A:
...     pass
>>> a = A()
>>> a.abcde = 1
>>> del a.abcdf
Traceback (most recent call last):
...
AttributeError: 'A' object has no attribute 'abcdf'. Did you mean: 'abcde'?

    (Contributed by Nikita Sobolev and Pranjal Prajapati in gh-136588.)

  • Several error messages incorrectly using the term "argument" have been corrected. (Contributed by Stan Ulbrych in gh-133382.)

其他语言特性修改

  • Python now uses UTF-8 as the default encoding, independent of the system's environment. This means that I/O operations without an explicit encoding, for example, open('flying-circus.txt'), will use UTF-8. UTF-8 is a widely-supported Unicode character encoding that has become a de facto standard for representing text, including nearly every webpage on the internet, many common file formats, programming languages, and more.

    This only applies when no encoding argument is given. For best compatibility between versions of Python, ensure that an explicit encoding argument is always provided. The opt-in encoding warning can be used to identify code that may be affected by this change. The special encoding='locale' argument uses the current locale encoding, and has been supported since Python 3.10.

    To retain the previous behaviour, Python's UTF-8 mode may be disabled with the PYTHONUTF8=0 environment variable or the -X utf8=0 command-line option.

    参见

    PEP 686 for further details.

    (Contributed by Adam Turner in gh-133711; PEP 686 written by Inada Naoki.)

  • The interpreter help (such as python --help) is now in color. This can be controlled by environment variables. (Contributed by Hugo van Kemenade in gh-148766.)

  • Unraisable exceptions are now highlighted with color by default. This can be controlled by environment variables. (Contributed by Peter Bierma in gh-134170.)

  • More color in argparse, ast, calendar, difflib, http.server, pickletools, PyREPL tab completion, python --help, sqlite3, timeit, tokenize, unraisable exceptions and stdlib (ast, compileall, doctest, gzip, inspect, json.tool, pdb, profiling.sampling, random, regrtest, sqlite3, timeit, tokenize, trace, unittest, uuid, zipapp, zipfile) CLI help.

  • The __repr__() of ImportError and ModuleNotFoundError now shows "name" and "path" as name=<name> and path=<path> if they were given as keyword arguments at construction time. (Contributed by Serhiy Storchaka, Oleg Iarygin, and Yoav Nir in gh-74185.)

  • The __dict__ and __weakref__ descriptors now use a single descriptor instance per interpreter, shared across all types that need them. This speeds up class creation, and helps avoid reference cycles. (Contributed by Petr Viktorin in gh-135228.)

  • The -W option and the PYTHONWARNINGS environment variable can now specify regular expressions instead of literal strings to match the warning message and the module name, if the corresponding field starts and ends with a forward slash (/). (Contributed by Serhiy Storchaka in gh-134716.)

  • Functions that take timestamp or timeout arguments now accept any real numbers (such as Decimal and Fraction), not only integers or floats, although this does not improve precision. (Contributed by Serhiy Storchaka in gh-67795.)

  • Added bytearray.take_bytes(n=None, /) to take bytes out of a bytearray without copying. This enables optimizing code which must return bytes after working with a mutable buffer of bytes such as data buffering, network protocol parsing, encoding, decoding, and compression. Common code patterns which can be optimized with take_bytes() are listed below.

    建议的优化重构

    描述

    旧消息

    New

    Return bytes after working with bytearray

    		 
    def read() -> bytes:
    buffer = bytearray(1024)
    ...
    return bytes(buffer)

    def read() -> bytes:
    buffer = bytearray(1024)
    ...
    return buffer.take_bytes()

    Empty a buffer getting the bytes

    		 
    buffer = bytearray(1024)
...
data = bytes(buffer)
buffer.clear()

    buffer = bytearray(1024)
...
data = buffer.take_bytes()

    Split a buffer at a specific separator

    		 
    buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = bytes(buffer[:n + 1])
del buffer[:n + 1]
assert data == b'abc\n'
assert buffer == bytearray(b'def')

    buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = buffer.take_bytes(n + 1)

    Split a buffer at a specific separator; discard after the separator

    		 
    buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = bytes(buffer[:n])
buffer.clear()
assert data == b'abc'
assert len(buffer) == 0

    buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
buffer.resize(n)
data = buffer.take_bytes()

    (Contributed by Cody Maloney in gh-139871.)

  • Many functions related to compiling or parsing Python code, such as compile(), ast.parse(), symtable.symtable(), and importlib.abc.InspectLoader.source_to_code(), now allow the module name to be passed. It is needed to unambiguously filter syntax warnings by module name. (Contributed by Serhiy Storchaka in gh-135801.)

  • Allowed defining the __dict__ and __weakref__ __slots__ for any class. (Contributed by Serhiy Storchaka in gh-41779.)

  • Allowed defining any __slots__ for a class derived from tuple (including classes created by collections.namedtuple()). (Contributed by Serhiy Storchaka in gh-41779.)

  • The slice type now supports subscription, making it a generic type. (Contributed by James Hilton-Balfe in gh-128335.)

  • The class memoryview now supports the float complex and double complex C types: formatting characters 'Zf' and 'Zd' respectively. (Contributed by Victor Stinner in gh-146151 and gh-148675.)

  • Allow the count argument of bytes.replace() to be a keyword. (Contributed by Stan Ulbrych in gh-147856.)

  • Unary plus is now accepted in match literal patterns, mirroring the existing support for unary minus. (Contributed by Bartosz Sławecki in gh-145239.)

  • The import system now acquires per-module locks in hierarchical order (parent packages before their submodules). This fixes a long-standing deadlock where one thread importing pkg.sub and another importing pkg.sub.mod could each block the other when pkg/sub/__init__.py imports pkg.sub.mod. (Contributed by Gregory P. Smith in gh-83065.)

默认的交互式 shell

新增模块

math.integer

This module provides access to the mathematical functions for integer arguments (PEP 791). (Contributed by Serhiy Storchaka in gh-81313.)

改进的模块

argparse

  • The BooleanOptionalAction action now supports single-dash long options and alternate prefix characters. (Contributed by Serhiy Storchaka in gh-138525.)

  • Changed the suggest_on_error parameter of argparse.ArgumentParser to default to True. This enables suggestions for mistyped arguments by default. (Contributed by Jakob Schluse in gh-140450.)

  • Added backtick markup support in ArgumentParser description and epilog text to highlight inline code when color output is enabled. (Contributed by Savannah Ostrowski in gh-142390.)

  • Extended backtick markup to argument help text and added support for double backticks (RST inline-literal style). (Contributed by Hugo van Kemenade in gh-149375.)

array

  • Support the float complex and double complex C types: formatting characters 'Zf' and 'Zd' respectively. (Contributed by Victor Stinner in gh-146151 and gh-148675.)

  • Support half-floats (16-bit IEEE 754 binary interchange format): formatting character 'e'. (Contributed by Sergey B Kirpichev in gh-146238.)

  • The array.typecodes type changed from str to tuple to support type codes longer than 1 character (Zf and Zd). (Contributed by Victor Stinner in gh-148675.)

ast

  • Add color parameter to dump(). If True, the returned string is syntax highlighted using ANSI escape sequences. If False (the default), colored output is always disabled. (Contributed by Stan Ulbrych in gh-148981.)

  • The command-line output is now syntax highlighted by default. This can be controlled using environment variables. (Contributed by Stan Ulbrych in gh-148981.)

asyncio

  • Added TaskGroup.cancel to allow early termination of a task group, for instance, when the goal of the tasks has been achieved or their services are no longer needed. Previously this would involve unintuitive boilerplate such as an extra task raising a custom exception which is then suppressed as it exits the task group. (Contributed by John Belmonte in gh-127214.)

base64

binascii

calendar

collections

  • Added collections.Counter.__xor__() and collections.Counter.__ixor__() to compute the symmetric difference between Counter objects. (Contributed by Raymond Hettinger in gh-138682.)

concurrent.futures

  • Improved error reporting when a child process in a concurrent.futures.ProcessPoolExecutor terminates abruptly. The resulting traceback will now tell you the PID and exit code of the terminated process. (Contributed by Jonathan Berg in gh-139486.)

contextlib

dataclasses

  • Annotations for generated __init__ methods no longer include internal type names.

dbm

  • Added new reorganize() methods to dbm.dumb and dbm.sqlite3 to recover unused free space previously occupied by deleted entries. (Contributed by Andrea Oliveri in gh-134004.)

difflib

email

  • Email generators now raise an error when an EmailMessage cannot be accurately flattened due to a non-ASCII email address (mailbox) in an address header. Options for supporting Email Address Internationalization (EAI) are discussed in EmailPolicy.utf8. (Contributed by R David Murray and Mike Edmunds in gh-122540.)

faulthandler

functools

gc

  • Python 3.14.0-3.14.4 shipped with a new incremental garbage collector. However, due to a number of reports of significant memory pressure in production environments, it has been reverted back to the generational GC from 3.13. This is the GC now used in Python 3.14.5 and later and Python 3.15.

hashlib

  • Ensure that hash functions guaranteed to be always available exist as attributes of hashlib even if they will not work at runtime due to missing backend implementations. For instance, hashlib.md5 will no longer raise AttributeError if OpenSSL is not available and Python has been built without MD5 support. (Contributed by Bénédikt Tran in gh-136929.)

http.client

  • A new max_response_headers keyword-only parameter has been added to HTTPConnection and HTTPSConnection constructors. This parameter overrides the default maximum number of allowed response headers. (Contributed by Alexander Enrique Urieles Nieto in gh-131724.)

http.server

importlib.metadata

  • Previously, when accessing a distribution metadata directory not containing a metadata file, metadata() and Distribution.metadata() would return an empty PackageMetadata object as if the file was present but empty. Now, a MetadataNotFound exception is raised. See importlib_metadata#493 for background and rationale and and gh-143387 for rationale on the compatibility concerns. (Contributed by Jason R. Coombs.)

inspect

  • Add parameters inherit_class_doc and fallback_to_class_doc for getdoc(). (Contributed by Serhiy Storchaka in gh-132686.)

json

  • Add the array_hook parameter to load() and loads() functions: allow a callback for JSON literal array types to customize Python lists in the resulting decoded object. Passing combined frozendict to object_pairs_hook param and tuple to array_hook will yield a deeply nested immutable Python structure representing the JSON data. (Contributed by Joao S. O. Bueno in gh-146440.)

locale

math

mimetypes

mmap

  • mmap.mmap now has a trackfd parameter on Windows; if it is False, the file handle corresponding to fileno will not be duplicated. (Contributed by Serhiy Storchaka in gh-78502.)

  • Added the mmap.mmap.set_name() method to annotate an anonymous memory mapping if Linux kernel supports PR_SET_VMA_ANON_NAME (Linux 5.17 or newer). (Contributed by Donghee Na in gh-142419.)

os

  • Add os.statx() on Linux kernel versions 4.11 and later with glibc versions 2.28 and later. (Contributed by Jeffrey Bosboom and Victor Stinner in gh-83714.)

  • os.makedirs() function now has a parent_mode parameter that allows specifying the mode for intermediate directories. This can be used to match the behavior from Python 3.6 and earlier by passing parent_mode=mode. (Contributed by Zackery Spytz and Gregory P. Smith in gh-86533.)

os.path

pdb

  • Use the new interactive shell as the default input shell for pdb. (Contributed by Tian Gao in gh-145379.)

pickle

  • Add support for pickling private methods and nested classes. (Contributed by Zackery Spytz and Serhiy Storchaka in gh-77188.)

pickletools

pprint

re

  • re.prefixmatch() and a corresponding re.Pattern.prefixmatch() have been added as alternate, more explicit names for the existing and now soft deprecated re.match() and re.Pattern.match() APIs. These are intended to be used to alleviate confusion around what match means by following the Zen of Python's "Explicit is better than implicit" mantra. Most other language regular expression libraries use an API named match to mean what Python has always called search. (Contributed by Gregory P. Smith in gh-86519.)

resource

shelve

  • Added new reorganize() method to shelve used to recover unused free space previously occupied by deleted entries. (Contributed by Andrea Oliveri in gh-134004.)

  • Add support for custom serialization and deserialization functions in the shelve module. (Contributed by Furkan Onder in gh-99631.)

socket

  • Add constants for the ISO-TP CAN protocol. (Contributed by Patrick Menschel and Stefan Tatschner in gh-86819.)

sqlite3

  • The command-line interface has several new features:

    • SQL keyword completion on <tab>. (Contributed by Long Tan in gh-133393.)

    • Prompts, error messages, and help text are now colored. This is enabled by default, see 控制颜色 for details. (Contributed by Stan Ulbrych and Łukasz Langa in gh-133461.)

    • Table, index, trigger, view, column, function, and schema completion on <tab>. (Contributed by Long Tan in gh-136101.)

ssl

  • Indicate through ssl.HAS_PSK_TLS13 whether the ssl module supports "External PSKs" in TLSv1.3, as described in RFC 9258. (Contributed by Will Childs-Klein in gh-133624.)

  • Added new methods for managing groups used for SSL key agreement

    • ssl.SSLContext.set_groups() sets the groups allowed for doing key agreement, extending the previous ssl.SSLContext.set_ecdh_curve() method. This new API provides the ability to list multiple groups and supports fixed-field and post-quantum groups in addition to ECDH curves. This method can also be used to control what key shares are sent in the TLS handshake.

    • ssl.SSLSocket.group() returns the group selected for doing key agreement on the current connection after the TLS handshake completes. This call requires OpenSSL 3.2 or later.

    • ssl.SSLContext.get_groups() returns a list of all available key agreement groups compatible with the minimum and maximum TLS versions currently set in the context. This call requires OpenSSL 3.5 or later.

    (Contributed by Ron Frederick in gh-136306.)

  • Added a new method ssl.SSLContext.set_ciphersuites() for setting TLS 1.3 ciphers. For TLS 1.2 or earlier, ssl.SSLContext.set_ciphers() should continue to be used. Both calls can be made on the same context and the selected cipher suite will depend on the TLS version negotiated when a connection is made. (Contributed by Ron Frederick in gh-137197.)

  • Added new methods for managing signature algorithms:

    (Contributed by Ron Frederick in gh-138252.)

subprocess

  • subprocess.Popen.wait(): when timeout is not None and the platform supports it, an efficient event-driven mechanism is used to wait for process termination:

    If none of these mechanisms are available, the function falls back to the traditional busy loop (non-blocking call and short sleeps). (Contributed by Giampaolo Rodola in gh-83069.)

symtable

sys

  • Add sys.abi_info namespace to improve access to ABI information. (Contributed by Klaus Zimmermann in gh-137476.)

sys.monitoring

tarfile

threading

timeit

  • The output of the timeit command-line interface is colored by default. This can be controlled with environment variables. (Contributed by Hugo van Kemenade in gh-146609.)

  • The command-line interface now colorizes error tracebacks by default. This can be controlled with environment variables. (Contributed by Yi Hong in gh-139374.)

  • Make the target time of timeit.Timer.autorange() configurable and add --target-time option to the command-line interface. (Contributed by Alessandro Cucci and Miikka Koskinen in gh-80642.)

tkinter

  • The tkinter.Text.search() method now supports two additional arguments: nolinestop which allows the search to continue across line boundaries; and strictlimits which restricts the search to within the specified range. (Contributed by Rihaan Meher in gh-130848.)

  • A new method tkinter.Text.search_all() has been introduced. This method allows for searching for all matches of a pattern using Tcl's -all and -overlap options. (Contributed by Rihaan Meher in gh-130848.)

  • Added new methods pack_content(), place_content() and grid_content() which use Tk commands with new names (introduced in Tk 8.6) instead of *_slaves() methods which use Tk commands with outdated names. (Contributed by Serhiy Storchaka in gh-143754.)

  • Added Event attributes user_data for Tk virtual events and detail for Enter, Leave, FocusIn, FocusOut, and ConfigureRequest events. (Contributed by Matthias Kievernagel and Serhiy Storchaka in gh-47655.)

tokenize

tomllib

  • The tomllib module now supports TOML 1.1.0. This is a backwards compatible update, meaning that all valid TOML 1.0.0 documents are parsed the same way.

    The changes, according to the official TOML changelog, are:

    • Allow newlines and trailing commas in inline tables.

      Previously an inline table had to be on a single line and couldn't end with a trailing comma. This is now relaxed so that the following is valid:

      tbl = {
   key      = "a string",
   moar-tbl =  {
      key = 1,
   },
}

    • Add \xHH notation to basic strings for codepoints under 255, and the \e escape for the escape character:

      null = "null byte: \x00; letter a: \x61"
csi = "\e["

    • Seconds in datetime and time values are now optional. The following are now valid:

      dt = 2010-02-03 14:15
t  = 14:15

    (Contributed by Taneli Hukkinen in gh-142956.)

types

typing

  • PEP 747: Add TypeForm, a new special form for annotating values that are themselves type expressions. TypeForm[T] means "a type form object describing T (or a type assignable to T)". At runtime, TypeForm(x) simply returns x, which allows explicit annotation of type-form values without changing behavior.

    This helps libraries that accept user-provided type expressions (for example int, str | None, TypedDict classes, or list[int]) expose precise signatures:

    from typing import Any, TypeForm

def cast[T](typ: TypeForm[T], value: Any) -> T: ...

    (Contributed by Jelle Zijlstra in gh-145033.)

  • PEP 728: Add support in TypedDict for the closed and extra_items class arguments. A closed TypedDict does not allow extra keys beyond those specified in the class body, while a TypedDict with extra_items allows arbitrary extra items where the values are of the specified type. (Contributed by Angela Liss in gh-137840.)

  • Code like class ExtraTypeVars(P1[S], Protocol[T, T2]): ... now raises a TypeError, because S is not listed in Protocol parameters. (Contributed by Nikita Sobolev in gh-137191.)

  • Code like class B2(A[T2], Protocol[T1, T2]): ... now correctly handles type parameters order: it is (T1, T2), not (T2, T1) as it was incorrectly inferred at runtime before. (Contributed by Nikita Sobolev in gh-137191.)

  • PEP 800: Add @typing.disjoint_base, a new decorator marking a class as a disjoint base. This is an advanced feature primarily intended to allow type checkers to faithfully reflect the runtime semantics of types defined as builtins or in compiled extensions. If a class C is a disjoint base, then child classes of that class cannot inherit from other disjoint bases that are not parent or child classes of C. (Contributed by Jelle Zijlstra in gh-148639.)

  • TypeVarTuple now accepts bound, covariant, contravariant, and infer_variance keyword arguments, matching the interface of TypeVar and ParamSpec. bound semantics remain undefined in the specification.

unicodedata

unittest

urllib.parse

venv

  • On POSIX platforms, platlib directories will be created if needed when creating virtual environments, instead of using a lib64 -> lib symlink. This means purelib and platlib of virtual environments no longer share the same lib directory on platforms where sys.platlibdir is not equal to lib. (Contributed by Rui Xi in gh-133951.)

warnings

  • Improve filtering by module in warnings.warn_explicit() if no module argument is passed. It now tests the module regular expression in the warnings filter not only against the filename with .py stripped, but also against module names constructed starting from different parent directories of the filename (with /__init__.py, .py and, on Windows, .pyw stripped). (Contributed by Serhiy Storchaka in gh-135801.)

wave

(Contributed by Lionel Koenig and Michiel W. Beijen in gh-60729.)

webbrowser

  • On macOS, the new webbrowser.MacOS class opens URLs via /usr/bin/open instead of constructing and executing AppleScript via osascript. The default browser is detected from the LaunchServices preferences file using plistlib, with com.apple.Safari as the fallback on fresh installations. For non-HTTP(S) URLs, open -b <bundle-id> is used to route the URL through a browser rather than the OS file handler, preventing file injection attacks. (Contributed by Jeff Lyon in gh-137586.)

xml

  • Add the xml.is_valid_name() function to check whether a string can be used as an element or attribute name in XML. (Contributed by Serhiy Storchaka in gh-139489.)

  • Add the xml.is_valid_text() function, which allows to check whether a string can be used in the XML document. (Contributed by Serhiy Storchaka in gh-139489.)

xml.parsers.expat

zlib

性能优化

base64 & binascii

  • CPython's underlying base64 implementation now encodes 2x faster and decodes 3x faster thanks to simple CPU pipelining optimizations. (Contributed by Gregory P. Smith and Serhiy Storchaka in gh-143262.)

  • Implementation for Ascii85, Base85, and Z85 encoding has been rewritten in C. Encoding and decoding is now two orders of magnitude faster and consumes two orders of magnitude less memory. (Contributed by James Seo and Serhiy Storchaka in gh-101178.)

  • Implementation for Base32 has been rewritten in C. Encoding and decoding is now two orders of magnitude faster. (Contributed by James Seo in gh-146192.)

csv

Upgraded JIT compiler

Results from the pyperformance benchmark suite report 8-9% geometric mean performance improvement for the JIT over the standard CPython interpreter built with all optimizations enabled on x86-64 Linux. On AArch64 macOS, the JIT has a 12-13% speedup over the tail calling interpreter with all optimizations enabled. The speedups for JIT builds versus no JIT builds range from roughly 15% slowdown to over 100% speedup (ignoring the unpack_sequence microbenchmark) on x86-64 Linux and AArch64 macOS systems.

注意

These results are not yet final.

The major upgrades to the JIT are:

  • LLVM 21 build-time dependency

  • New tracing frontend

  • Basic register allocation in the JIT

  • More JIT optimizations

  • GDB and GNU backtrace() unwinding support

  • Better machine code generation

LLVM 21 build-time dependency

The JIT compiler now uses LLVM 21 for build-time stencil generation. As always, LLVM is only needed when building CPython with the JIT enabled; end users running Python do not need LLVM installed. Instructions for installing LLVM can be found in the JIT compiler documentation for all supported platforms. (Contributed by Savannah Ostrowski in gh-140973.)

A new tracing frontend

The JIT compiler now supports significantly more bytecode operations and control flow than in Python 3.14, enabling speedups on a wider variety of code. For example, simple Python object creation is now understood by the 3.15 JIT compiler. Overloaded operations and generators are also partially supported. This was made possible by an overhauled JIT tracing frontend that records actual execution paths through code, rather than estimating them as the previous implementation did. (Contributed by Ken Jin in gh-139109. Support for Windows added by Mark Shannon in gh-141703.)

Basic register allocation in the JIT

A basic form of register allocation has been added to the JIT compiler's optimizer. This allows the JIT compiler to avoid certain stack operations altogether and instead operate on registers. This allows the JIT to produce more efficient traces by avoiding reads and writes to memory. (Contributed by Mark Shannon in gh-135379.)

More JIT optimizations

More constant-propagation is now performed. This means when the JIT compiler detects that certain user code results in constants, the code can be simplified by the JIT. (Contributed by Ken Jin and Savannah Ostrowski in gh-132732.)

Reference counts are avoided whenever it is safe to do so. This generally reduces the cost of most operations in Python. (Contributed by Ken Jin, Donghee Na, Zheao Li, Hai Zhu, Savannah Ostrowski, Reiden Ong, Noam Cohen, Tomas Roun, PuQing, Cajetan Rodrigues, and Sacul in gh-134584.)

By tracking unique references to objects, the JIT optimizer can now eliminate reference count updates and perform in-place operations on ints and floats. (Contributed by Reiden Ong, and Pieter Eendebak in gh-143414 and gh-146306.)

The JIT optimizer now supports significantly more operations than in 3.14. (Contributed by Kumar Aditya, Ken Jin, Jiahao Li, and Sacul in gh-131798.)

GDB and GNU backtrace() unwinding support

The JIT compiler now publishes unwind information for generated machine code to the GDB interface on supported Linux ELF platforms. When libgcc frame registration is available, the same unwind information is also registered for GNU backtrace() stack walkers. This allows native debuggers, crash handlers, and diagnostic tools using these mechanisms to unwind through JIT frames instead of stopping at generated code. (Contributed by Diego Russo and Pablo Galindo Salgado in gh-146071 and gh-149104.)

Better machine code generation

The JIT compiler's machine code generator now produces better machine code for x86-64 and AArch64 macOS and Linux targets. In general, users should experience lower memory usage for generated machine code and more efficient machine code versus 3.14. (Contributed by Brandt Bucher in gh-136528 and gh-135905. Implementation for AArch64 contributed by Mark Shannon in gh-139855. Additional optimizations for AArch64 contributed by Mark Shannon and Diego Russo in gh-140683 and gh-142305.)

Maintainability

The JIT optimizer's operations have been simplified. This was made possible by a refactoring of JIT data structures. (Contributed by Zhongtian Zheng in gh-148211 and Hai Zhu in gh-143421.)

移除

ast

  • The constructors of AST nodes now raise a TypeError when a required argument is omitted or when a keyword argument that does not map to a field on the AST node is passed. These cases had previously raised a DeprecationWarning since Python 3.13. (Contributed by Brian Schubert and Jelle Zijlstra in gh-137600 and gh-105858.)

collections.abc

  • collections.abc.ByteString has been removed from collections.abc.__all__. collections.abc.ByteString has been deprecated since Python 3.12, and is scheduled for removal in Python 3.17.

ctypes

datetime

  • strptime() now raises ValueError when the format string contains %d (day of month) without a year directive. This has been deprecated since Python 3.13. (Contributed by Stan Ulbrych and Gregory P. Smith in gh-70647.)

glob

  • Removed the undocumented glob.glob0() and glob.glob1() functions, which have been deprecated since Python 3.13. Use glob.glob() and pass a directory to its root_dir argument instead. (Contributed by Barney Gale in gh-137466.)

http.server

  • Removed the CGIHTTPRequestHandler class and the --cgi flag from the python -m http.server command-line interface. They were deprecated in Python 3.13. (Contributed by Bénédikt Tran in gh-133810.)

importlib.resources

pathlib

  • pathlib.Path.mkdir() now has a parent_mode parameter that allows specifying the mode for intermediate directories when parents=True. (Contributed by Gregory P. Smith in gh-86533.)

  • Removed deprecated pathlib.PurePath.is_reserved(). Use os.path.isreserved() to detect reserved paths on Windows. (Contributed by Nikita Sobolev in gh-133875.)

平台

  • Removed the platform.java_ver() function, which was deprecated since Python 3.13. (Contributed by Alexey Makridenko in gh-133604.)

sre_*

  • Removed sre_compile, sre_constants and sre_parse modules. (Contributed by Stan Ulbrych in gh-135994.)

sysconfig

threading

  • Remove support for arbitrary positional or keyword arguments in the C implementation of RLock objects. This was deprecated in Python 3.14. (Contributed by Bénédikt Tran in gh-134087.)

types

typing

  • typing.ByteString has been removed from typing.__all__. typing.ByteString has been deprecated since Python 3.9, and is scheduled for removal in Python 3.17.

  • The undocumented keyword argument syntax for creating NamedTuple classes (for example, Point = NamedTuple("Point", x=int, y=int)) is no longer supported. Use the class-based syntax or the functional syntax instead. (Contributed by Bénédikt Tran in gh-133817.)

  • Using TD = TypedDict("TD") or TD = TypedDict("TD", None) to construct a TypedDict type with zero fields is no longer supported. Use class TD(TypedDict): pass or TD = TypedDict("TD", {}) instead. (Contributed by Bénédikt Tran in gh-133823.)

  • Deprecated typing.no_type_check_decorator() has been removed. (Contributed by Nikita Sobolev in gh-133601.)

wave

  • Removed the getmark(), setmark() and getmarkers() methods of the Wave_read and Wave_write classes, which were deprecated since Python 3.13. (Contributed by Bénédikt Tran in gh-133873.)

zipimport

弃用

新的弃用

  • ast

    • 创建抽象 AST 节点 (如 ast.AST 或 ast.expr) 的做法已被弃用并将在 Python 3.20 中引发错误。

      (Contributed by Brian Schubert in gh-116021.)

  • base64:

    • Accepting the + and / characters with an alternative alphabet in b64decode() and urlsafe_b64decode() is now deprecated. In future Python versions they will be errors in the strict mode and discarded in the non-strict mode. (Contributed by Serhiy Storchaka in gh-125346.)

  • CLI:

    • Deprecate -b and -bb command-line options and schedule them to become no-ops in Python 3.17. These were primarily helpers for the Python 2 -> 3 transition. Starting with Python 3.17, no BytesWarning will be raised for these cases; use a type checker instead.

      (Contributed by Nikita Sobolev in gh-136355.)

  • collections.abc

    • The following statements now cause DeprecationWarnings to be emitted at runtime:

      • from collections.abc import ByteString

      • import collections.abc; collections.abc.ByteString.

      DeprecationWarnings were already emitted if collections.abc.ByteString was subclassed or used as the second argument to isinstance() or issubclass(), but warnings were not previously emitted if it was merely imported or accessed from the collections.abc module.

  • hashlib:

    • In hash function constructors such as new() or the direct hash-named constructors such as md5() and sha256(), the optional initial data parameter could also be passed as a keyword argument named data= or string= in various hashlib implementations.

      Support for the string keyword argument name is now deprecated and is slated for removal in Python 3.19. Prefer passing the initial data as a positional argument for maximum backwards compatibility.

      (Contributed by Bénédikt Tran in gh-134978.)

  • http.cookies:

  • imaplib:

    • Altering IMAP4.file is now deprecated and slated for removal in Python 3.19. This property is now unused and changing its value does not explicitly close the current file.

  • re:

    • re.match() and re.Pattern.match() are now soft deprecated in favor of the new re.prefixmatch() and re.Pattern.prefixmatch() APIs, which have been added as alternate, more explicit names. These are intended to be used to alleviate confusion around what match means by following the Zen of Python's "Explicit is better than implicit" mantra. Most other language regular expression libraries use an API named match to mean what Python has always called search.

      We do not plan to remove the older match() name, as it has been used in code for over 30 years. Code supporting older versions of Python should continue to use match(), while new code should prefer prefixmatch(). See prefixmatch() vs. match().

      （由 Gregory P. Smith 在 gh-86519 以及 Hugo van Kemenade 在 gh-148100 中贡献。）

  • struct:

    • Calling Struct.__new__() without a required argument is now deprecated and will be removed in Python 3.20. Calling the __init__() method on an initialized Struct object is deprecated and will be removed in Python 3.20.

      （由 Sergey B Kirpichev 和 Serhiy Storchaka 在 gh-143715 中贡献。）.)

    • Using 'F' and 'D' type codes now are soft deprecated in favor of two-letter forms 'Zf' and 'Zd'. (Contributed by Sergey B Kirpichev in gh-121249.)

  • typing:

    • The following statements now cause DeprecationWarnings to be emitted at runtime:

      • from typing import ByteString

      • import typing; typing.ByteString.

      DeprecationWarnings were already emitted if typing.ByteString was subclassed or used as the second argument to isinstance() or issubclass(), but warnings were not previously emitted if it was merely imported or accessed from the typing module.

  • webbrowser:

    • webbrowser.MacOSXOSAScript is deprecated in favour of webbrowser.MacOS and scheduled for removal in Python 3.17. (Contributed by Jeff Lyon in gh-137586.)

  • __version__

计划在 Python 3.16 中移除

计划在 Python 3.17 中移除

  • datetime:

    • 使用不带年份的包含 %e (月份日期序号) 的格式字符串的 strptime() 调用自 Python 3.15 起已被弃用。 （由 Stan Ulbrych 在 gh-70647 中贡献。）

  • collections.abc:

    • collections.abc.ByteString 计划在 Python 3.17 中移除。

      使用 isinstance(obj, collections.abc.Buffer) 来在运行时测试 obj 是否实现了 缓冲区协议。要用于类型标注，则使用 Buffer 或者显式指明你的代码所支持的类型的并集 (例如 bytes | bytearray | memoryview)。

      ByteString 原本是想作为 bytes 和 bytearray 的超类型的抽象基类提供。 不过，由于该 ABC 从未有过任何方法，知道一个对象是 ByteString 的实例并不能真正告诉你有关该对象的任何有用信息。 其他常见缓冲区类型如 memoryview 同样不能被当作是 ByteString 的子类型（无论是在运行时还是对于静态类型检查器）。

      请参阅 PEP 688 了解详情。 （由 Shantanu Jain 在 gh-91896 中贡献。）

  • encodings:

  • webbrowser:

    • webbrowser.MacOSXOSAScript 已被弃用并改用 webbrowser.MacOS。 (gh-137586)

  • typing:

    • 在 Python 3.14 之前，旧式的联合是通过私有类 typing._UnionGenericAlias 实现的。实现已不再需要该类，但为向后兼容性保留了该类，并计划在 Python 3.17 中删除。用户应使用记录在案的内省助手函数，如 typing.get_origin() 和 typing.get_args()，而不是依赖于私有的实现细节。

    • typing.ByteString 自 Python 3.9 起已被弃用，计划在 Python 3.17 中移除。

      使用 isinstance(obj, collections.abc.Buffer) 来在运行时测试 obj 是否实现了 缓冲区协议。要用于类型标注，则使用 Buffer 或者显式指明你的代码所支持的类型的并集 (例如 bytes | bytearray | memoryview)。

      ByteString 原本是想作为 bytes 和 bytearray 的超类型的抽象基类提供。 不过，由于该 ABC 从未有过任何方法，知道一个对象是 ByteString 的实例并不能真正告诉你有关该对象的任何有用信息。 其他常见缓冲区类型如 memoryview 同样不能被当作是 ByteString 的子类型（无论是在运行时还是对于静态类型检查器）。

      请参阅 PEP 688 了解详情。 （由 Shantanu Jain 在 gh-91896 中贡献。）

  • tkinter:

    • The tkinter.Variable methods trace_variable(), trace() (an alias of trace_variable()), trace_vdelete() and trace_vinfo(), deprecated since Python 3.14, are scheduled for removal in Python 3.17. Use trace_add(), trace_remove() and trace_info() instead. (Contributed by Serhiy Storchaka in gh-120220.)

计划在 Python 3.18 中移除

  • 当需要一个文件描述符时将不再接受布尔值。 （由 Serhiy Storchaka 在 gh-82626 中贡献。）

  • decimal:

    • 非标准且未写入文档的 Decimal 格式说明符 'N'，它仅在 decimal 模块的 C 实现中受到支持，自 Python 3.13 起已被弃用。 （由 Serhiy Storchaka 在 gh-89902 中贡献。）

  • 由 PEP 829 定义的弃用：

    • 在 name.pth 文件中的 import 行会被静默地忽略。

    （由 Barry Warsaw 在 gh-148641 中贡献。）

计划在 Python 3.19 中移除

  • ctypes:

    • 在非 Windows 平台上，通过设置 _pack_ 而非 _layout_，隐式切换到与 MSVC 兼容的结构布局。

  • hashlib:

    • 在哈希函数构造器如 new() 或者直接使用哈希算法名称的构造器如 md5() 和 sha256() 中，它们可选的初始数据形参在不同的 hashlib 实现中也可使用名为 data= 或 string= 的关键字参数形式传入。

      对 string 关键字参数名称的支持现已被弃用并计划在 Python 3.19 中移除。

      在 Python 3.13 之前，string 关键字形参没有根据哈希函数的后端实现得到正确的支持。 建议将初始数据作为位置参数传入以获得最大的向下兼容性。

  • http.cookies:

  • imaplib:

    • 修改 IMAP4.file 的做法现已被弃用并计划在 Python 3.19 中移除。 该属性现已不再使用并且修改其值不会自动关闭当前文件。

      Before Python 3.14, this property was used to implement the corresponding read() and readline() methods for IMAP4 but this is no longer the case since then.

Pending removal in Python 3.20

计划在未来版本中移除

以下 API 将会被移除，尽管具体时间还未确定。

  • argparse:

    • 嵌套参数组和嵌套互斥组已被弃用。

    • 将未写入文档的关键字参数 prefix_chars 传递给 add_argument_group() 的做法现在已被弃用。

    • argparse.FileType 类型转换器已弃用。

  • builtins:

    • 生成器: throw(type, exc, tb) 和 athrow(type, exc, tb) 签名已被弃用：请改用 throw(exc) 和 athrow(exc)，即单参数签名。

    • 目前 Python 接受数字类字面值后面紧跟关键字的写法，例如 0in x, 1or x, 0if 1else 2。它允许像 [0x1for x in y] 这样令人困惑且有歧义的表达式 (它可以被解读为 [0x1 for x in y] 或者 [0x1f or x in y])。如果数字类字面值后面紧跟关键字 and, else, for, if, in, is 和 or 中的一个将会引发语法警告。在未来的版本中它将改为语法错误。 (gh-87999)

    • 对 __index__() 和 __int__() 方法返回非 int 类型的支持：将要求这些方法必须返回 int 的严格子类的实例。

    • 对 __float__() 方法返回 float 的子类的支持：将要求这些方法必须返回 float 的实例。

    • 对 __complex__() 方法返回 complex 的子类的支持：将要求这些方法必须返回 complex 的实例。

    • 传入一个复数作为 complex() 构造器中的 real 或 imag 参数的做法现在已被弃用；它应当仅作为单个位置参数被传入。（由 Serhiy Storchaka 在 gh-109218 中贡献。）

  • calendar: calendar.January 和 calendar.February 常量已被弃用并由 calendar.JANUARY 和 calendar.FEBRUARY 替代。 （由 Prince Roshan 在 gh-103636 中贡献。）

  • codecs: codecs.open() 请改用 open() 。 (gh-133038)

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

  • datetime:

    • utcnow(): 使用 datetime.datetime.now(tz=datetime.UTC)。

    • utcfromtimestamp(): 使用 datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)。

  • gettext: 复数值必须是一个整数。

  • importlib:

  • importlib.metadata:

    • EntryPoints 元组接口。

    • 返回值中隐式的 None。

  • logging: warn() 方法自 Python 3.3 起已被弃用，请改用 warning().

  • mailbox: 对 StringIO 输入和文本模式的使用已被弃用，改用 BytesIO 和二进制模式。

  • os: 在多线程的进程中调用 os.register_at_fork()。

  • os.path: os.path.commonprefix() 已弃用，对于路径前缀请使用 os.path.commonpath()。 os.path.commonprefix() 函数被弃用是由于其误导性的名称和模块。 使用该函数获取路径前缀是不安全的，尽管它被包括在一个用于操作路径的模块中，使用此函数很容易意外地将路径遍历安全漏洞引入 Python 程序中。

  • pydoc.ErrorDuringImport: 使用元组值作为 exc_info 形参的做法已被弃用，应使用异常实例。

  • re: 现在对于正则表达式中的数字分组引用和分组名称将应用更严格的规则。现在只接受 ASCII 数字序列作为数字引用。 字节串模式和替换字符串中的分组名称现在只能包含 ASCII 字母和数字以及下划线。 （由 Serhiy Storchaka 在 gh-91760 中贡献。）

  • shutil: rmtree() 的 onerror 形参在 Python 3.12 中已被弃用；请改用 onexc 形参。

  • ssl 选项和协议：

    • ssl.SSLContext 不带 protocol 参数的做法已被弃用。

    • ssl.SSLContext: set_npn_protocols() 和 selected_npn_protocol() 已被弃用：请改用 ALPN。

    • ssl.OP_NO_SSL* 选项

    • ssl.OP_NO_TLS* 选项

    • ssl.PROTOCOL_SSLv3

    • ssl.PROTOCOL_TLS

    • ssl.PROTOCOL_TLSv1

    • ssl.PROTOCOL_TLSv1_1

    • ssl.PROTOCOL_TLSv1_2

    • ssl.TLSVersion.SSLv3

    • ssl.TLSVersion.TLSv1

    • ssl.TLSVersion.TLSv1_1

  • threading 的方法：

  • typing.Text (gh-92332).

  • 内部类 typing._UnionGenericAlias 不再用于实现 typing.Union。 为了保持与使用该私有类的用户的兼容性，将至少在 Python 3.17 之前提供兼容性垫片。 （由 Jelle Zijlstra 在 gh-105499 中贡献。）

  • unittest.IsolatedAsyncioTestCase: 从测试用例返回不为 None 的值的做法已被弃用。

  • urllib.parse 已弃用的函数：改用 urlparse()

    • splitattr()

    • splithost()

    • splitnport()

    • splitpasswd()

    • splitport()

    • splitquery()

    • splittag()

    • splittype()

    • splituser()

    • splitvalue()

    • to_bytes()

  • wsgiref: SimpleHandler.stdout.write() 不应执行部分写入。

  • xml.etree.ElementTree: 对 Element 进行真值检测已被弃用。在未来的发布版中它将始终返回 True。建议改用显式的 len(elem) 或 elem is not None 检测。

  • sys._clear_type_cache() 已弃用，请改用 sys._clear_internal_caches()。

软弃用

尚无计划移除 soft deprecated API。

  • re.match() and re.Pattern.match() are now soft deprecated in favor of the new re.prefixmatch() and re.Pattern.prefixmatch() APIs, which have been added as alternate, more explicit names. These are intended to be used to alleviate confusion around what match means by following the Zen of Python's "Explicit is better than implicit" mantra. Most other language regular expression libraries use an API named match to mean what Python has always called search.

    We do not plan to remove the older match() name, as it has been used in code for over 30 years. Code supporting older versions of Python should continue to use match(), while new code should prefer prefixmatch(). See prefixmatch() vs. match().

    （由 Gregory P. Smith 在 gh-86519 以及 Hugo van Kemenade 在 gh-148100 中贡献。）

  • Using 'F' and 'D' format type codes of the struct module now are soft deprecated in favor of two-letter forms 'Zf' and 'Zd'. (Contributed by Sergey B Kirpichev in gh-121249.)

C API 的变化

新的特性

被改变的 C API

被移除的 C API

  • 移除已弃用的 PyUnicode 函数：

    • PyUnicode_AsDecodedObject(): 改用 PyCodec_Decode()。

    • PyUnicode_AsDecodedUnicode(): 改用 PyCodec_Decode()；请注意某些编解码器 (例如 "base64") 可能返回 str 以外的类型，比如 bytes。

    • PyUnicode_AsEncodedObject(): 改用 PyCodec_Encode()。

    • PyUnicode_AsEncodedUnicode(): 改用 PyCodec_Encode()；请注意某些编解码器 (例如 "base64") 可能返回 bytes 以外的类型，比如 str。

    （由 Stan Ulbrych 在 gh-133612 中贡献。）

  • PyImport_ImportModuleNoBlock(): 已弃用的 PyImport_ImportModule() 的别名。 （由 Bénédikt Tran 在 gh-133644 中贡献。）

  • PyWeakref_GetObject() 和 PyWeakref_GET_OBJECT: 改用 PyWeakref_GetRef()。 在 Python 3.12 及更旧的版本中可以使用 pythoncapi-compat project 来获取 PyWeakref_GetRef()。 （由 Bénédikt Tran 在 gh-133644 中贡献。）

  • 移除了已弃用了 PySys_ResetWarnOptions()。 改为清除 sys.warnoptions 和 warnings.filters。

    （由 Nikita Sobolev 在 gh-138886 中贡献。）

以下函数已被移除而应改用 PyConfig_Get()。 在 Python 3.13 及更旧的版本中可以使用 pythoncapi-compat project 来获取 PyConfig_Get()。

已弃用的 C API

构建的改变

  • Removed implicit fallback to the bundled copy of the libmpdec library. Now this should be explicitly enabled with --with-system-libmpdec set to no or with --without-system-libmpdec. (Contributed by Sergey B Kirpichev in gh-115119.)

  • The new configure option --with-missing-stdlib-config=FILE allows distributors to pass a JSON configuration file containing custom error messages for standard library modules that are missing or packaged separately. (Contributed by Stan Ulbrych and Petr Viktorin in gh-139707.)

  • The new configure option --with-pymalloc-hugepages enables huge page support for pymalloc arenas. When enabled, arena size increases to 2 MiB and allocation uses MAP_HUGETLB (Linux) or MEM_LARGE_PAGES (Windows) with automatic fallback to regular pages. On Windows, use build.bat --pymalloc-hugepages. At runtime, huge pages must be explicitly enabled by setting the PYTHON_PYMALLOC_HUGEPAGES environment variable to 1.

  • Annotating anonymous mmap usage is now supported if Linux kernel supports PR_SET_VMA_ANON_NAME (Linux 5.17 or newer). Annotations are visible in /proc/<pid>/maps if the kernel supports the feature and -X dev is passed to the Python or Python is built in debug mode. (Contributed by Donghee Na in gh-141770.)

  • CPython is now built with frame pointers enabled by default (PEP 831). Pass --without-frame-pointers to opt out.

    Authors of C extensions and native libraries built with custom build systems should ensure the unwind chain is intact. This is usually done by adding -fno-omit-frame-pointer and similar flags to CFLAGS. See --without-frame-pointers documentation for the specific flags Python uses.

    (Contributed by Pablo Galindo Salgado and Savannah Ostrowski in gh-149201.)

  • 64-bit builds using Visual Studio 2026 (MSVC 18) may now use the new tail-calling interpreter. Results on Visual Studio 18.1.1 report between 15-20% speedup on the geometric mean of pyperformance on Windows x86-64 over the switch-case interpreter on an AMD Ryzen 7 5800X. We have observed speedups ranging from 14% for large pure-Python libraries to 40% for long-running small pure-Python scripts on Windows. This was made possible by a new feature introduced in MSVC 18, which the official Windows 64-bit binaries on python.org now use. (Contributed by Chris Eibl, Ken Jin, and Brandt Bucher in gh-143068. Special thanks to Steve Dower, and the MSVC team including Hulon Jenkins.)

移植到 Python 3.15

本节列出了先前描述的更改以及可能需要更改代码的其他错误修正。